Built some speaker with much awesome help from diyaudio members now I am hooked. I would like to eventually build an amp from scratch but since I can barely solder wires together I thought I would start with something easier. I purchased a couple of class d boards from a diy member. (ti 300 and sure ab013) Since this is a first project and the potential for smoke and maybe even fire is pretty high I do not want to spend too much and would like to use a transformer from a yamaha rxv 870 receiver. how do I tell the power of the transformer and which wires are what. or is that just not going to work.

'Time to read a basic electronics book before trying to proceed on 10 quick answers to simple questions. If books are not your
favourite read, try the appropriate articles listed on this site. Note that the voltage appropriate to your class D kit is unlikely
to be available in old class AB amplifiers with dual, +/- power supplies. Look at the info available for the kit and measure what
your amplifier's power supply provides (voltage across the main electrolytic capacitors). If it's not < the specified maximum,
you will be wasting your time trying to adapt it unless you can also build regulator circuits to force it within safe limits.

Playing with transformers and mains voltages to get a power supply is not safe for newbs or anyone without the experience
and the smarts to work safely. Read and heed the warnings as dead DIYs are not cool for the audio image.

Visit the class D and chipamp forums here and check out what is being used by people more likely doing what you are interested in.